code: def forward_cpu(self, inputs):
      self.retain_inputs((0,))
      x = inputs[0].reshape(len(inputs[0]), -1)
      return ((x * x).sum(axis=1),)
  
file_path: chainer/chainer/functions/math/batch_l2_norm_squared.py
imports: import six
  import chainer
  from chainer.backends import cuda
  from chainer import function_node
  from chainer.functions.math import sum
  from chainer.utils import type_check
label_desc: Use image node_id 2 for calling the BatchL2NormSquared obj's underlying member method code with example usage: obj.forward_cpu(inputs) and returns: unknown